by Thomas A. Schwartz

Most people in the construction industry have had this experience: Someone (a client, a guy at a cocktail party, your Aunt Ethel) asks, "Why can't you people build things the way you used to? Why do new buildings fall apart?"

Depending on the circumstances, the question is posed in tones ranging from outrage to jocularity to sincere curiosity. It could be easily dismissed as an unsophisticated query from someone who doesn't appreciate the complex art and science of construction today.

But it is based on a valid observation. We don't make buildings the way we used to. And sometimes we suffer the consequences.

Evolving Construction Techniques

In the first half of the 20th century, building facades underwent a transition from massive load-bearing walls to relatively thin, lightweight, non-load-bearing "curtain walls."

Before the transition, walls consisted of layers of masonry ("wythes"), which formed part of the load-bearing structure of the building. Floors were supported by the exterior walls and moved with the walls.

The masonry also provided resistance to water penetration, aided by design features such as belt courses and drip edges that reduced water flow over the facade and protected the more vulnerable joints. Any moisture that did migrate to the inside evaporated readily because of good ventilation.

These walls resisted deterioration because their materials had inherent durability and because their thermal mass mitigated temperature swings. But by today's standards, these walls were expensive, energy inefficient, and limited in design flexibility. Something else was needed — something that offered improved thermal performance, greater design freedom, and lower cost.

Chicago's Marshall Field Store by H. H. Richardson is an example of a 19th century structure whose massive load-bearing walls avoided many of the problems of today's curtain walls. Photo: Courtesy GreatBuildings.com The Hancock Building in Boston suffered one of the most infamous curtain wall failures. Photo: Michael Shellenbarger/ University of Oregon Library   Click on thumbnail images to view full-size pictures.